Been to Aruba 6 or 7 times. If you like a nice hotel I prefer the Marriott or the Hyatt in Aruba. Both are on the beach and I got the best deal by just calling the hotel, usually in the summer you get great deals and since they are south of the hurricane region then you don't have to be concerned about that. They have water sports available. The diving is very poor in Aruba, wind surfing was excellent. The Sonesta is downtown Oranjestad, didn't think much of it.
Only been to Curazao twice, (you can fly between the two) Diving was MUCH better. I stayed at the Plaza but that was downtown and kind of business oriented - just go to one of the diving focussed places.
Curacao Hotels Lions Dive and Beach Resort, a natural stay at resorts Much more Europeans in Curazao whereas Aruba is very American style.
If you want to dive, go to Bonaire, no question, but the only thing to do is diving, pretty much. I spent a week there diving twice a day and could easily have spent another week.